The results of this study indicate that, compared to placebo, boys in the higher-dose drisapersen group (6 mg/kg once weekly) experienced stabilization and even improvements in their muscle function and physical activity as measured by the six-minute walk test (6MWT) for the 24-week treatment phase and maintained this improvement during the 24-week follow-up period. Additionally, when evaluating the percent-predicted six-minute walk distance (6MWD), a clinically meaningful treatment difference of 5.2% was observed at week 24 and 4.8% at week 48.

Principal investigator, Craig M. McDonald, M.D., Professor and Chair of Physical Medicine & Rehabilitation and Professor of Pediatrics at the University of California, Davis School of Medicine, will report the 48 week results in a poster session (Abstract #50) today at the Muscular Dystrophy Association 2014 Clinical Conference in Chicago, Illinois (March 16-19).

"Given the severity of the disease and the lack of disease modifying treatment options available, the results of this important study support the use of drisapersen at a dose of 6 mg/kg once weekly in the treatment of boys with DMD eligible for exon 51 skipping" Dr. McDonald said. "The maintenance of the clinically meaningful treatment benefit in the 24-week follow-up phase is very encouraging evidence for the drug's ability to produce prolonged stabilization of disease and may indicate that, at the 6 mg/kg once weekly dose, the drug has a long term treatment effect that helps delay disease progression in younger, less severe boys."

The study included 51 boys with DMD who were at least five years old, still able to walk and stand up from the floor without help in less than 15 seconds. As previously reported, boys in the group who received a 6mg/kg dose of drisapersen each week for the 24-week treatment period show a 27.1 meter improvement in the 6MWT (including a 16.1 m increase from baseline) over the boys in the placebo group at the end of the treatment period (p=0.069), indicating a clinically meaningful outcome for the primary endpoint. This study compared 6mg/kg/week with 3mg/kg/week and placebo and was not statistically powered to show a significant difference between the arms. A clinically meaningful treatment difference of 27.9 m over placebo (p=0.177) was maintained for 24 weeks after drisapersen administration ceased. This includes an overall mean increase from baseline of 14.7 m. In the drisapersen 6 mg/kg/week group, an improvement was seen in the percent-predicted 6MWD of 5.2% (p=0.051) and 4.8% (p=0.154) when compared to placebo at weeks 24 and 48, respectively.

Drisapersen at weekly doses of 3 and 6 mg/kg/week was generally well tolerated, although the majority of subjects treated with drisapersen reported injection-site reactions (none severe or serious). Renal abnormalities were common and occurred both in the placebo and drisapersen groups.

"Our priority remains improving the lives and outcomes of boys afflicted with this devastating disease. We are encouraged by these results, and are actively continuing with the analysis of the total drisapersen data set, which includes 300 patients and combined data representing 450 patient years to put these results into context," said Hans Schikan, CEO of Prosensa. "As we reported earlier this year, initial findings from further analyses of the aggregate drisapersen data suggest that treating earlier in DMD and treating longer shows a delay in the progression of the disease."

A copy of the poster can be accessed (starting March 18) under "Events & Presentations" through the Investors & Media section of the Prosensa corporate website at www.prosensa.com.

LEIDEN, The Netherlands, March 18, 2014 (GLOBE NEWSWIRE) -- Prosensa Holding N.V. (Nasdaq:RNA), the Dutch biopharmaceutical company focusing on RNA-modulating therapeutics for rare diseases with high unmet need, today reported financial results for the full year ending December 31, 2013, and provided an update on the next steps for its exon-skipping platform for the treatment of Duchenne Muscular Dystrophy (DMD).

"As we have previously stated, we are encouraged by initial findings from further analyses of the aggregate drisapersen data that suggest that treating earlier in DMD and treating longer shows a delay in the progression of the disease. These data give us the confidence to engage patient groups, clinical experts and regulators to explore a path forward for drisapersen," said Hans Schikan, CEO of Prosensa.

Mr. Schikan continued, "While the past few months have been a very important transition period for Prosensa, our primary focus has not changed, which is to improve the lives and outcomes of boys with DMD. At the start of the year we regained the rights to drisapersen and retained rights to our other development-stage compounds for DMD from GlaxoSmithKline (GSK). We are currently working closely with GSK to transfer data and other elements covered in the collaboration as soon as practicable and within 120 days of the January 12 effective date of the agreement. Concurrently, we are focused on the continued analysis of the complete drisapersen data set, preparing for possible re-dosing of boys and having a meaningful dialogue with regulatory authorities. We expect to communicate the status of these events during the second quarter of this year."

With data from more than 300 patients, Prosensa has the largest clinical data set in DMD. The Company is actively working to define the most optimal path forward for its DMD pipeline, which includes formulating a re-dosing plan for boys who have previously participated in clinical trials. In addition, it has enrolled 190 patients in a planned 250 patient study to better understand the natural history of DMD and potential biomarkers. Prosensa's current portfolio of drug candidates includes six compounds for the treatment of DMD with four compounds currently in clinical development, all of which have received orphan drug status in the United States and the European Union. The compounds utilize an innovative technique called exon-skipping to provide a personalized medicine approach to treat different populations of DMD patients. Furthermore, the Company has progressed PROSPECT, a unique research program which could enable expedited development of DMD therapeutic candidates that target multiple exons.

At of the end of 2013, Prosensa had a cash position of €82.2 million.

Recent Corporate Highlights

-- Updates on the Drisapersen Development Program

On January 13, 2014, Prosensa and GlaxoSmithKline (GSK) announced that Prosensa regained all rights from GSK to drisapersen and retained rights to all other programs for the treatment of DMD. This transfer of rights represents the termination of the collaboration agreement between GSK and Prosensa executed in 2009 and gives Prosensa full, unencumbered rights to continue the development of drisapersen as well as each of its DMD programs.

On January 16, 2014, Prosensa announced initial findings from further analyses of the aggregate data obtained from the clinical development program of drisapersen for the treatment of DMD. The analyses, which are based on the results from three placebo controlled studies and two long term open label studies, suggest that treating earlier in DMD and treating longer shows a delay in the progression of the disease, as measured by the six-minute walk test (6MWT). Key safety findings are consistent with previous observations.

On February 18, 2014, the Investigational New Drug (IND) for drisapersen was transferred from GSK. As a first step in developing the path forward for drisapersen, Prosensa communicated to patient advocacy groups and investigators that it is exploring options for study participants to be re-dosed with drisapersen. Furthermore, it has initiated a survey to seek feedback from patients and investigators regarding the willingness and desire of patients to resume treatment. Based on the respondents to date, the majority of patients wish to be re-dosed with drisapersen.

-- Rare Disease Expert Joined Company Supervisory Board

On December 10, 2013, Prosensa announced that Dr. Georges Gemayel, an expert in the rare disease space and strategic corporate leadership, was nominated for the Prosensa Supervisory Board. The appointment of Dr. Gemayel was approved in the extraordinary general meeting of shareholders on January 23, 2014.

-- New FP7 Grant Awarded for Development of DMD Imaging Biomarkers

On November 25, 2013, Prosensa and Newcastle University, UK, announced the award of a second Framework Programme 7 (FP7) research grant from the European Commission. This new FP7 research grant totals approximately €6 million to support the development of imaging biomarkers for DMD. The project "Developing imaging technologies for therapeutic interventions in rare diseases" will be known as "BIOIMAGE-NMD" and is expected to run for three and a half years. Earlier in the year, Prosensa was part of a pan-European consortium that received a €6 million FP7 research grant to support the ongoing clinical study of its third novel DMD development candidate, PRO045.

Financial Highlights

Cash Position and Cash Consumption: Prosensa's cash and cash equivalents as of December 31, 2013 were €82.2 million, compared to €40.7 million as of December 31, 2012 and €86.7 million as of the quarter ended September 30, 2013. The increase in cash and cash equivalents was due to €64.0 million in proceeds (before issuance cost) from the issuance of 6.9 million shares of common stock upon the IPO on July 3, 2013. The company's cash consumption, excluding cash flows from financing for the 12-months ended December 31, 2013 was €22.4 million.

Revenue: Revenue for the 12-months ended December 31, 2013 was €8.9 million, compared with €7.9 million in 2012 due to increased collaboration revenue of €1.2 million and lower license income of €0.1 million.

R&D Expense: Research and development expense was €18.5 million for the 12-months ended December 31, 2013, compared to €14.4 million for the comparable period in 2012. While we incurred expenses for preclinical safety studies for PRO045 and PRO053 in the 12-months ended December 31, 2012, our research and development expenses in 2013 mainly related to the ongoing Phase I/II study of PRO045 and PRO053. In the twelve months ended December 31, 2013 we also incurred expenses for the preclinical safety studies for PRO052, the Natural History and PROSPECT programs.

G&A Expense: General and administrative expense was €7.7 million for the 12-months ended December 31, 2013, compared to €4.0 million in 2012. The increase is primarily due to higher share-based compensation expense in 2013 of €1.1 million compared to €180 thousand in 2012 and costs associated with operating as a public company.

Net Loss: Net loss for the full year 2013 was €16.6 million or €0.51 per share, compared to €9.9 million or €0.37 per share for the full year 2012.

Upcoming Conferences

Prosensa management will be participating in the following conferences and events:

Orphan Disease Forum at the BIO International Convention, June 24, San Diego, CA

Conference Call / Webcast Information

Prosensa will host a conference call on March 18 at 8:00am ET, 1:00pm CET to discuss the full year 2013 financial results and a corporate update. In order to participate in the conference call, please dial 1-877-407-9170 (US domestic toll-free). International dial-in numbers and an audio webcast can be accessed under "Events & Presentations" through the Investors & Media section of the Prosensa corporate website www.prosensa.com.